Design and optimization of acoustic absorber with ultra–broadband below 1000 Hz

Abstract Although existing studies have realized broadband absorption in different frequency ranges, achieving high-efficiency absorption across the entire 100 Hz to 1000 Hz band remains a challenge. In this work, we propose a coupled spiral porous lining metamaterial (SPLM) with air slits and attached porous material, exhibiting ultra-broadband sound absorption below 1000 Hz. The absorption coefficient of the SPLM can be calculated based on dual-porosity theory, whose accuracy is rigorously verified through simulations and experiments. Combining the theoretical model with the genetic algorithm, the coupled SPLM is automatically optimized, achieving a balance between increasing energy loss and decreasing resonant frequency by adjusting the coupling strength among the unit structures. The optimized structure achieves the absorption coefficient above 0.8 in the range from 82 Hz to 1000 Hz, with an average absorption coefficient of 0.86 and a relative bandwidth of 170%. This work provides a practical and generalizable strategy for the tailored optimization of ultra-broadband acoustic metamaterials at low frequencies, which can also be extended to other target frequency bands.